Tatooine Times Two: Amateur Astronomers Find Planet in Four-Star System

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Tatooine Times Two: Amateur Astronomers Find Planet in Four-Star System

Update: A second team has also reported independent confirmation of the new exoplanet. Details below the original story.

A group of volunteers using a citizen science astronomy website have discovered an extrasolar planet orbiting a record four stars.

Scarcely a year ago, astronomers weren't sure if planets could exist in binary star systems, where two stars orbit one another. But after the discovery of a circumbinary exoplanet – which would have two suns in its sky, much like the famous Tatooine of Star Wars – scientists realized that such worlds were possible and have found at least five more similar systems. About half of stars in the universe are found in binary pairs and if they can host planets then the chances for life outside our own world may be greatly increased.

The newly discovered exoplanet orbits within a quadruple star system named KIC 4862625 that is about 3,200 light-years from Earth. Citizen scientists Kian Jek of San Francisco and Robert Gagliano of Cottonwood, Arizona, used the website Planethunters.org to scan data from these stars captured by NASA's Kepler space telescope and noticed a periodic dip in their light.

The data showed that a planet was passing in front of its parent stars, a binary pair, every 138 days and eclipsing their light. The planet has been dubbed PH1 (Planet Hunters 1) and is estimated to be a gas giant with a radius 6.2 times that of Earth, making it slightly bigger than Neptune, and a mass roughly half that of Jupiter. The binary stars have about 1.5 and 0.41 times the mass of the sun and orbit one another with a period of 20 days.

PH1's binary pair parents are in turn orbited by another binary pair of stars at a distance 1,000 times that between the Earth and the sun. If any beings could live on PH1, they would not only witness a double sunset but might also be able to spot two bright stars in their night sky wandering against the background stars.

Update: An independent analysis, led by graduate astronomy student Veselin Kostov at Johns Hopkins University, also found evidence for an exoplanet within the quadruple star system. Independent confirmation of a result is an important part of the scientific process and this is one of the fastest independently confirmed exoplanets to date.

Kostov's analysis matches up extremely closely with the Yale team's results, independently determining the exoplanet's mass and orbit despite having less data. The paper will be up on the arxiv preprint server later today and has also been submitted to The Astrophysical Journal.

While Kostov knew that KIC 4862625 was a binary system, he was unable to determine that it was a quadruple system. When he saw the Yale team's results, "I freaked out," said Kostov. "The fact that these things exist is just mind blowing."